Stress has many important implications for mental health. Increased stress usually results in elevation of glucocorticoid hormones, which, among many other effects, could have an impact on memory and the brain. The proposed research concerns two types of stress, nutritional (metabolic), which is usually caused by nutritional deficits, and psychosocial, which could be caused by social interactions. The main goal of the proposed study is to investigate how nutritional and social stress are mediated by stress hormones, and their effects on memory and hippocampal plasticity using mountain chickadees and scrub jays. Specific Aim 1 will examine whether corticosterone is directly involved in mediating memory performance and neurogenesis in the avian hippocampus on short- and long-term basis by using corticosterone implants. Specific aim 2 will investigate whether social dominance interactions result in increased stress in subordinate individuals and whether such stress is associated with increased levels of stress hormones and corresponding changes in memory and the hippocampus. Specific aim 3 will test the hypothesis that nutritional stress during development results in increased levels of stress hormones and in deteriorated memory performance and changes in the hippocampal formation during the adulthood. First, young birds will receive a restricted diet during their development and after becoming nutritionally independent their memory performance, levels of corticosterone and neurogenesis rates will be compared with those of young receiving ad libitum diet. Second, all young will be fed ad libitum during their development, but half of the birds will receive food containing corticosterone whereas the other half will receive food containing placebo. Memory performance and neurogenesis rates of both groups will be compared after birds become nutritionally independent. This study will provide important insights into how social and nutritional stress can affect levels of corticosterone, and how such changes mediate alterations in memory and neural plasticity in adult animals. This study will add to our knowledge of the effects of stress on mental health and will help us to understand the evolution and adaptive significance of stress responses.